Beneficiation of minerals



'1. M. LE BARQN BENEFICIATION 0F MINERALS June 2, 1959 2 Sheets-Sheet 1Filed Sept. 22, 1955 F'lELl J 1959 l. M. LE BARON ,889,042

BENEFICIATION OF MINERALS Filed Sept. 22, 1955 2 Sheets-Sheet 2 FIE-Egym/KM atent iii 2,889,042 Patented June 2, 1959 BENEFICIATIDN F IraMilton Le Baron, Evanston, Ill., assignor to International Minerals &Chemical Corporation, a corporation of New York Application September22, 1955, Serial No. 535,839 4 Claims. (Cl. 209-127) This inventionrelates to a method for concentrating mineral components. Moreparticularly, it relates to the beneficiation of ore by the separationof the desired mineral from gangue material. Still more particularly, itrelates to the beneficiatiou of phosphate and potash ores.

It has long been known that it is possible to beneficiate minerals byelectrostatic methods. However, up to the present time, electrostaticmethods have been successful from an economic and practical standpointonly in isolated instances. Generally, the apparatus has comprisedessentially paired and opposited charged electrodes.

An essential problem in this field is the shortness of time during whichthe electrostatic field influences particles being separated. This shortperiod of effective operation necessitates use of a multiplicity ofstages for effective concentration. Electrostatic roll separators whichseparate particles according to their conductivity characteristicsrevolve at, for example, 6 rpm. and the particles are in theelectrostatic field for about /6 of the circumferential length of aroll. When utilizing the method wherein the particles pass as freelyfalling particles through the electrostatic field, the force of gravityaccelerates the speed of the particles to a point where multiple stagesare markedly more effective than an elongated field.

It is a primary object of this invention to overcome the shortcomingsand disadvantages of the-prior electrostatic separation systems.

It is another object of this invention to provide a system whereby thetime in the electrostatic afield is under direct control.

It is a further object of this invention to provide apparatus forelectrostatically separating materials in which the material issupported for the desired period in the electrostatic field andparticles differentially charged move in diverse directions for separatecollection.

These and other objects of the invention will be apparent to thoseskilled in the art fronrthe following de :scription.

In carrying out the instant invention, comminuted ore material issupported on a continuous non-conductor belt moving at a rate designedto :give the desired holding time in the electrostatic field. Above andadjacent to this support belt and moving in a transverse direction isasec- 0nd non-conductor belt. An electrostatic field is maintained inthe area where the belts overlap. It will, of course, he understood thatthe electrostatic field area may be enlarged by the positioning of amultiplicity of belts in parallel in each direction.

The electrostatic field may be developed between electrodes positionedso that the belts are intermediate the electrodes or the beltsthemselves may be the electrodes if the belts are operating on the wellknown Van de Graaff system.

For effective separation, it is necessary that the particles bedifferentially charged before entering the electrostatic field.Differential charge in the instant process is I an acceptance ordivesting of electrons, as the case may be, so that at least one of thecomponents of the mixture to be separated possesses a definite chargeand is not merely polarized as in the case of pyroelectric crysstals.Differential charging can be brought about by agitation of a propercharacter or by subjecting the material to contact with a source of freeelectrons such as is supplied by the earth, with or without the aid ofheating. It is preferred, that the mixture or ore either while in aheated condition or while in a surface dry condition, be subjected toactivity such as to bring about adequate differential charging thru oneor the other or a combination of the above methods assuring thatelectron exchange will take place and that the particles will be chargedas aforesaid.

Certain electrical conductive materials when grounded to the earth willfacilitate the transfer of electrons to one or the other component of amixture. In this regard, material comprising essentially carbon, forexample, graphite is one of the best materials for donating electrons toheated phosphate ore gangue. Other useful materials for chargingphosphate ore are zinc, galvanized iron, and 'brass. In addition to theabove, aluminum is an excellent donor element for the charging of potashore components. Such donor element may be a ground plate, chute, tray,hopper, rotating bowl or the like.

Heating of the particles may be carried out in suitable equipment suchas an electric oven, heat exchanger and the like to reduce the granularmaterial to dryness. Preferably the materials are heated to atemperature in the range between 150 F. and about 550 F. with a holdingtime sufiicient to insure dryness. This material while at thesetemperatures or at any time before the particles pick up surfacemoisture are charged as hereinbefore described and passed thru anelectrostatic field.

The elficiency of the process is to a degree dependent upon particlesize of the materials being separated. The most satisfactory range froman economic standpoint is that obtained by grinding material to a sizebetween about -4 and about 200 mesh. Particle size to which the materialmust be ground is of course dependent upon liberation of the componentsdesired to be concentrated from the gangue. In the case of phosphateore, grinding is usually carried to the point such that of the materialwill be in the range of about l4/ +150 mesh standard screen size. Thesame mesh size, is in general, useful for potash ores such as sylviniteand mixed ores, although a narrower mesh size range is preferred wherepractical, generally of the order of 8/ mesh.

It is preferred though not essential in the interest of economy, whenbenficiating ores to use indirect methods of heating such as hot air,electric furnaces, or electric heating.

In the instant process, due consideration must be given to the method ofcreating the electrostatic field to which the aforesaid charged ore issubjected. In this process, it is desirable to apply a system which willminimize the possibility of altering the previously described chargewith corona discharge or normal induction such as is employed insubstantially all conductivity electrostatic separators. The electrodesshould "be kept at a high direct voltage potential substantially free ofalternating current com onents.

The strength of the electrostatic field which will effectively transferore particles from the supporting belt to the transverse removal beltwill vary with the average particle size and the type of material. Thefieldgradient or strength may vary from about 1000 to about 5000 voltsper inch of distance :between :belts in separating materials ofrelatively fineparticlesize land from :about 3000 to about 12000 voltsper inch for beneficiating of coarser particles. In general, it ispreferred to operate with total impressed differences of potential inthe range between about 30,000 volts and about 250,000 volts. Thisvoltage should be maintained in the form of direct current potentialsubstantially free of alternating current components, i.e., filtered DC.current low in so-called A.C. ripple. A steady supply of DC. voltagemay, for example, be obtained without expensive filtering apparatus bythe use of such equipment as rectified radio frequency power supply.

The belts, i.e., the support belt and the transverse removal belt may bemade up of any non-conductor material, for example, the belt may be madeup of synthetic fiber material such as Dacron, nylon, or the like, aswell as felt, velvet or satin.

It is to be noted that the instant process may be applied to minerals ormixtures of chemicals and different materials at various stages ofcommercially employed methods of beneficiating since no reagentizing isneeded to eifect separation. Thus the instant novel process hasapplication to ground Florida phosphate pebble, deslimed phosphate wastedebris, hard rock phosphate such as Montana and Tennessee phosphateores, potash ores such ,as cylvinite, langbeinite and mixed ores,feldspar ores,

chalcopyrite ore, fluorite ore, barite ore, and/ or mixtures thereof,and the like to give but a few illustrations. The apparatus of theinstant invention will be understood by reference to the drawingssetting forth a preferred embodiment of the invention in which:

Figure I is a front elevational view depicting a simplified schematicdiagram of the apparatus.

Figure II is a side elevational view of the same sche" matic apparatusillustration.

Referring to the drawings, the numeral 10 designates a support belt towhich the feed is delivered by a shaking or vibrating feeder 11 such asSyntron feeder having an iron trough. This iron trough is grounded tothe earth by electrical conductor 12.

Belt 10 is a continuous belt supported by a head pulley 13 and a tailpulley 14, said head pulley being driven at suitable speed by suitabledrive means such as a belt. Each pulley is supported by insulatormounts, 15 and 16 respectively. Intermediate pulleys 13 and 14 ispositioned an electrode 17 suitably connected by a conductor to a sourceof DC. power not shown.

Mounted above and generally within about 1 to inches of belt is belt 20,illustrated as being in the transverse position. Belt 20 is supported byhead pulley 21 and tail pulley 22, head pulley 21 being driven atsuitable speed by suitable drive means such as a belt. Pulleys 21 and 22are suspended by insulator mounts 2.3 and 24 respectively. Mounted so asto be shielded by belt 20 is an electrode 25 suitably connected by aconductor to the above mentioned source of D.C. power so as to be ofopposite polarity from electrode 17 or to ground.

Material discharged from belt 10 may go directly to a storage collectoror, as illustrated, the material may pass as freely falling bodiesbetween a pair of fixed electrodes 26 and 27 between which there isimposed an electrostatic field. Material is collected in receivers 28and 29 as middling and a concentrate of either the desired component orthe gangue material.

Material pinned to belt 20 upon leaving the electrostatic field fallsoff the belt and is collected in a hopper for disposal.

The invention will be more fully understood by study of the followingexample which is given by way of illustration and without any intentionthat the invention be limited thereto.

EXAMPLE I Florida pebble phosphate ore was hydraulically treated andscreened to remove pebble material. Deslirned washer debris of aparticle size in the range of 35/ +200 mesh standard screen size washeated in an electric oven to about 300 F.

Hot dry solids were delivered to the support belt at a. rate of about500 lbs. per hour .by means of a Syntron Table A Percent Percent weightBPL Feed. 29. 5 Tail 46. 7 3. 2 Middlin 36. 9 45. 0 Connnnh'n ta 17. 456. 0

EXAMPLE 11 Mixed ore from Eddy County, New Mexico, was crushed, groundon a hammer mill and screened on a Hummer Screen to produce a comminutedmaterial of 14 mesh size. The 14 mesh material was heated to 900 F. andcooled to about 300 F.

The cooled material was fed to the crossed Dacron belt separatordescribed above at a rate of 300 lbs. per hour by a vibrating Syntronfeeder equipped with a Lucite pan.

Electrodes were maintained at a difference of potential of about 20,000volts, the electrode behind the upper belt being the negative electrodeand the bottom electrode the positive electrode.

Results are indicated in Table B.

Having thus indicated the nature of my invention, what I claim is:

1. The process of concentrating granular mixtures of chemicallydifierent materials which comprises inducing said granular material toaccept differential electrical charges, delivering said charged materialonto a continuous non-conductor moving support member, moving saidcharged material into an electrostatic field supported on saidcontinuous non-conductor moving support member, moving transversely tosaid support member a second continuous non-conductor member adjacent toand above said moving support whereby the electrostatic field will causeone component of the mixture to transfer to said second non-conductorand separately collecting the materials from each continuous member.

2. The process of concentrating ore material which comprises deliveringdifferentially charged comminuted ore onto a continuous non-conductormoving support, moving said charged ore into a vertically alignedelectrostatic field on said continuous non-conductor moving support,moving a like non-conductor moving support through the electrostaticfield transversely to the movement of the ore supporter, said transversemoving support being positioned adjacent to and above the supportedmaterial, collecting the material after passage through theelectrostatic field as it is discharged from the moving support andcollecting material removed from the electrostatic field on thetransverse moving support as it is released by the support upon leavingthe electrostatic field.

3. Apparatus for electrostatically separating mixtures of chemicallydifferent materials which comprises continuous non-conductor movingbelts arranged to move in directions transverse to one another havingopposed faces one above the other, means for driving said moving belts,means for establishing an electrostatic field between said opposedfaces, agitating and feeding means for delivering material to beseparated onto the lower of said belts outside of said electrostaticfield, and collection hoppers for separated material.

4. Apparatus for electrostatically separating mixtures of chemicallydifferent materials which comprises continuous non-conductor movingbelts positioned one above the other and having opposed faces adjacentand transversely positioned relative to one another, means for drivingsaid moving belts, electrodes positioned above the 0pposed face of thetop belt and below the opposed face of 15 the bottom belt, means forestablishing an electrostatic field between said electrodes, agitatingand feeding means for delivering material to be separated onto the lowerof said belts outside of said electrostatic field, a collection hopperbelow the upper belt and adjacent the electrostatic field, andcollection hoppers adjacent the end of the lower belt.

References Cited in the file of this patent UNITED STATES PATENTS959,646 Swart May 31, 1910 2,223,476 Amstuz Dec. 3, 1940 2,328,577Oglesby Sept. 7, 1943 2,738,067 Cook Mar. 13, 1956 FOREIGN PATENTS598,948 Germany lune 21, 1934 870,831 Germany Mar. 16, 1953 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,889,042 June2, 1959 Ira Milton Le Baron It is hereby certified that error appears inthe-printed specification of the above numbered patent requiringcorrection and that the said Letters Patent should read as correctedbelow.

Column 1, line 25, for "opposited" read oppositely column 3 line 22 forcylvinite" read sylvinite line 65, for c-zxample which is" read exampleswhich are Signed and sealed this 16th day of February 1960..

(SEAL) Attest:

KARL H. AXLINE Attesting Officer ROBERT C. WATSON Commissioner ofPatents

